With concern over the ultimate exhaustion of energy sources such as fossil fuels a prime motivating factor, considerable attention has been given to the possible utilization of solar energy as a substitute energy source. As a result of that attention, a substantial amount of inventive effort has been expended in attempts to develop more efficient solar heaters for such diverse applications as home and commercial heating, industrial and agriculture processing and swimming-pool heating.
Older prior art solar water heaters disclosed costly, heavy and cumbersome combinations of metal pipes, heat absorbers, reflectors and glass heat-trapping windows.
More recently disclosed solar water heater concepts have employed modern plastic materials to minimize the cost and weight of the heaters. One disadvantage of some such plastic solar heaters is their inability to withstand even the moderate internal fluid pressures required to support reasonably high fluid flow rates through the heater.
High fluid flow rates are desirable because their use results in a rapid conduction of heat away from the solar energy absorbing surface of the heater, resulting in a relatively low surface temperature. The low surface temperature minimizes energy losses from the surface. This is because radiation losses are proportional to the fourth power of the surface temperature, while convection losses are nearly proportional to the first power of the temperature, and conduction losses are proportional to the first power of the surface temperature.
The present invention utilizes a novel extruded plastic semi-rigid configuration capable of sustaining the relatively high internal fluid pressures necessary for maintaining substantially high fluid flow rates.
Another novel and useful feature of the present invention is a ridged heat-absorbing surface which affords efficient solar energy absorption over a wide range of sun azimuth angles.
The present invention also employs a novel inlet manifold and outlet manifold configuration which assures substantially uniform sharing of the fluid mass flow rates by each flow conducting channel through the heater panels, thus assuring a uniformly low heater surface temperature to minimize radiation and convection losses. A novel reservoir section between the inlet manifold and channel entrances helps to maintain a relatively constant fluid flow rate through the panels despite variations in the pressure of the fluid supplied to the inlet manifold.